At present, to adapt the wheels to the axles, closed metal rings or plastic bushings are used, which are cemented to the wheel hubs so as to reduce play between hub and axles and to set the hubs with respect to the axles.
This wheel centering method has some drawbacks with regard to the mounting speed and correct wheel setting.
Substantial time is needed to cement the bushings or rings on the wheel hub, with a consequent increase in labor costs, and even then the setting obtained depends very much on the experience and ability of the operator.
Further, there is an increase in relative play between the parts since not only is there the normal play necessary for the introduction of the axle into the wheel, there is also the play necessary for the introduction of the bushing on the wheel hub, not to mention allowance for the error due to the distribution of the layer of cement used for the fixing.
Another method used for equipping vehicles with wheels having hubs that are of substantially greater diameter than the axle of the vehicle (or in any case where there is a certain play between hub and wheel axle) is that described in U.S. Pat. No. 2,969,256, filed on the 24th Feb. 1958, which envisages an interpositioning between the axle and wheel of a first ring having an external diameter which is about equal to the internal diameter of the hub, and which has an internal diameter which can be keyed onto the axle on which the wheel in being mounted. Any free space between the first above ring and the axle is overcome by the use of one or more second rings, having a circular transversal section with a diameter equal to the distance between the axle and the internal diameter of the ring. The association between the rings is guaranteed by welding them together. This procedure implies long mounting times, rendering the method disadvantageous.
One attempt at solving this problem is proposed by German patent no. 3,233,807, filed on the 11th Sep. 1982. This patent proposes a wheel which can be adapted to a plurality of different vehicles, providing a hub dimensioned according to the maximum diameter of the axles to be equipped, and a ring which is interplaced between the hub and the wheel axle to occupy the space due to the difference in diameter between the hub and axles with a smaller diameter than the largest of the group.
A drawback in this approach is the small contact surface that exists between the elements: indeed, the elastic ring adheres to small portions of the hub axial development and the axle. Since, therefore, only a part of the breadth of the hub and axle actually interact, which part corresponds more or less to the limited breadth of the ring, the solution proposed by the open ring of the above invention can give rise to instability.